Incandescent light bulbs create light by conducting electricity through a resistive filament and heating the filament to a very high temperature to produce visible light. Incandescent bulbs are made in a wide range of sizes and voltages. The bulbs typically include an enclosure with a tungsten filament inside and a base connector that provides both an electrical and structural support connection. Incandescent bulbs generally mate with a lamp socket having a threaded Edison base connector, bayonet base connector, pin base connector, or any suitable connector for providing electrical power to the bulb. However, incandescent light bulbs are generally inefficient and require frequent replacement. These lamps are in the process of being replaced by more efficient types of electric light such as fluorescent lamps, high-intensity discharge lamps, and, in particular, lamps with light emitting diode (LED) light sources.
LED technology continues to advance resulting in improved efficiencies and lower costs with LED light sources found in lighting applications ranging from small pin point sources to stadium lights. An LED light source is generally powered by an LED driver circuit that converts alternating current (AC) mains power to a constant current applied to LEDs within the LED light source. The LED driver circuit typically includes support circuitry and a microcontroller that may be programmable for different AC mains input requirements and different output voltages and currents.
The LED driver circuit may also include a primary circuit connected to an AC supply and a control side, isolated from the primary circuit. In some implementations, the control side may be isolated from the primary circuit in accordance with certain industry standards, for example, International Electrotechnical Commission (IEC) Class II, where the secondary side may also be referred to as being double insulated. In many implementations, the microcontroller for controlling the LED driver circuit may be located on the primary circuit in order to more efficiently monitor line input voltage and current, control the power factor presented to the AC supply, and perform other maintenance functions. However, as a result, programming the microcontroller, or reading data stored in the microcontroller memory, normally requires application of AC power to the primary circuit of the LED driver circuit in order to supply power to the microprocessor. This in turn may require incorporating additional procedures and additional safety measures, in particular when programming the microcontroller or attempting to read data from the microcontroller memory during production, installation, or service operations. For example, access to the primary side of the LED driver with wiring other than the AC line to provide power can be unsafe since the circuit is class 1 rated. Such access would require additional certification and installations guidelines to insure safety.
It would be advantageous to provide power to a microprocessor of an LED driver circuit without applying AC power to the primary circuit.